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O: Fachverband Oberflächenphysik

O 48: Poster Session - Electronic Structure of Surfaces: Spectroscopy, Surface States

O 48.10: Poster

Dienstag, 17. März 2020, 18:15–20:00, P2/EG

Ordered and disordered Tellurium surface alloys on Ag(111) and Cu(111) — •Andreas Raabgrund, Maximilian Ammon, Tilman Kisslinger, Lutz Hammer, and M. Alexander Schneider — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany

The formation of (surface) metal alloys using Te achieved a lot attention lately, e.g. for photovoltaics [1] or for spintronics [2]. In this work the Te surface alloys on Cu(111) and on Ag(111) were studied by low temperature STM, STS, LEED (all at 80 K) and DFT. Evaporation of Θ=1/3 ML Te leads to the formation of a (√3×√3)R30^∘ superstructure on Ag(111) [3] and a (2√3×√3)R30^∘ superstructure on Cu(111), respectively. By reducing the Te coverage we observe for both substrates patches of a disordered phase instead of a phase separation into ordered structure and clean surface. The reduced order below 1/3 ML Te coverage manifests itself as an increased background signal in LEED and is shown by STM to arise from a disordered Te lattice. Investigating those surface alloys by STS shows for both ordered structures a strong signal above the Fermi energy with onsets at 0.6...0.7 eV for AgTe and at 1.3...1.4 eV for CuTe, respectively. These features are also found by DFT and are the result of the longe-range order since they are absent on the disordered structures.
[1] Ibers J., Nat. Chem. 1, 508 (2009)
[2] Eremeev et al., Phys. Rev. Lett. 108, 246802 (2018)
[3] Liu et al, J. Phys. Chem. Lett. 2019, 10, 1866-1871 (2019)